The present invention relates to an improved threaded connection.
Threaded connections are known—see e.g., U.S. Pat. No. 5,282,707. Threads employed in such connections can be formed, for example, using metric ISO standard thread, which has gained widespread use.
With conventional threaded connections, the use of materials of different strengths for the male threads and female threads can result in damage to the threaded part formed from the lower-strength material when the threaded connection is overtightened. For this reason, it is standard practice for technical specifications to include the highest permissible tightening torques for threaded connections in order to avoid damage. In many cases, however, such as, for example, when replaceable cartridges are being screwed on, as in the case of air dryers in compressed-air brake systems for commercial vehicles, or even oil filters, it is standard practice to tighten the threaded connection by hand, without using a preadjustable torque wrench. Also, it is generally desirable in other applications of threaded connections to prevent accidental damage, such as can occur due to incorrect adjustment of a torque wrench or inadvertent failure to use a torque wrench.